Batteries are indispensable parts in electronic devices and more particularly in portable electronic products. It's very convenient to use an electronic device to digital camera, a toy or a remote controller etc.) with a battery, because the battery can independently provide power to the electronic device. At present, there are mainly two types of batteries. One type is traditional batteries. The traditional batteries have standard shapes and standard sizes, such as AA or AAA cylinder-shaped batteries with rating voltage of 1.5 volts. In most cases, this kind of batteries is a dry battery. fewer cases, this kind of battery is a nickel-cadmium or hydrogen-nickel rechargeable battery with rating voltage of 1.2 volts. Another type is a battery for an exclusive application. This kind of batteries is manufactured by different suppliers or is using for different products, thus, it has different shapes and sizes. In most cases, this kind of batteries has a rating voltage of 3 volts or 3.6 volts. Among this kind of batteries, lithium batteries with the rating voltage of 3.6 volts or 3.7 volts are most widely used.
Shapes and sizes of the traditional batteries must follow technical standards. It is convenient for widely manufacturing and widely using. A traditional battery has a good commonality. However, expenditure of using disposable dry batteries is large. It is not economic for a consumer to use lots of disposable dry batteries. Further, discarded batteries would pollute the environment. As to the nickel-cadmium or hydrogen-nickel batteries, they have memory effects and short cycle lives. Meanwhile, discarded batteries polluting the environment are still problems needed to solve.
Lithium-ion batteries have features of high energy density, long service times, no memory effects, long cycle lives, free of heavy metal. The lithium-ion batteries substitute the traditional dry batteries gradually. However, shapes and sizes of the lithium-ion batteries are so different that they have poor commonality. It is not convenient that consumers have to buy suitable batteries in a specialty store. Further, because of the lithium-ion batteries outputting high voltage, the lithium-ion batteries are not suitable for electronic products of low voltage requirements. Therefore, the lithium-ion batteries still can't substitute all the traditional dry batteries nowadays. It's hard to promote the using of the lithium-ion batteries.